This invention relates to a system for limiting the plays of tape cassettes, such as video cassettes, and more particularly to a system for counting the number of times the tape is played, or partially played, and to stop any further playing after a predetermined number of plays.
Mechanisms have been proposed for counting the number of times a video cassette has been used or played, and displaying the count for the purpose of computing a rental charge. See U.S. Pat. Nos. 3,995,319, 4,475,222, 4,575,778 and 4,586,101. A mechanism has also been proposed in U.S. Pat. No. 4,466,584, which will limit the total number of plays. The system in that patent uses an escapement to count the number of plays. A tape feeler assembly provides the escapement with the necessary cyclic motion as the tape is played and rewound. Once a predetermined number of plays have been counted, the mechanism locks to prevent further playing by providing a wheel locked to the escapement with an abutment.
A major disadvantage of that escapement system is inherent in the nature of an escapement; the mass of the base to which tape feelers are connected may be caused to oscillate, and thus advance the count wheel, if the cassette is jarred. It is for that reason that escapements are generally used only in systems that are handled with care, such as a clock, or that are so installed as to not be subject to being jarred. Another disadvantage is that locking the escapement, or a wheel connected to it, will not prevent further play; it will simply increase the drag on the reels. Such drag, if sufficient to prevent normal speed of the tape, may cause damage to the playback mechanism.
Advantages of an arrangement for counting and limiting the maximum number of times a video cassette may be played are that the rental charge of a video cassette may be based upon the number of times it is played, and the distributor of the rental video cassette may limit the number of times it is played to protect the proprietor of copyrighted material recorded on the tape. However, such an arrangement has many problems to be considered. If the mechanism is set to advance the count only at either extreme of play and rewind, the intent of the mechanism is easily defeated by avoiding the beginning and end during successive replays. To set it to advance at some intermediate point is not the solution either, for that prevents the viewer from enjoying a legitimate replay of a scene spanning that point.
Another problem is concerned with how easily the system may be defeated, such as by inserting a probe into the cassette to release the lock mechanism, or resetting the counter, after which the cassette will replay at least one other time, or replay the entire predetermined number of the authorized times.